1. Field of the Invention
The present invention relates to a recording head and a recording apparatus using it and, more particularly, to a recording head of an ink jet type in which an ink is ejected using thermal energy, and a recording apparatus using it.
2. Related Background Art
In a recording head of the ink jet type in which recording is performed using thermal energy, a heating element is arranged on a flow path communicating with an ejection outlet for ejecting an ink droplet. This heating element is energized for about several xcexc sec to generate bubbles in the ink and eject ink droplets, thereby performing recording. In this recording head, large numbers of ejection outlets and heating elements can be easily arranged at a high density to enable recording of a high-resolution image.
If all the heating elements of this recording head are simultaneously driven, a current flowing at once increases. Normally, several ten or hundred heating elements are divided into about 4 to 8 blocks, and driving timings for the respective blocks are slightly shifted from each other to suppress the current flowing at to be small.
If lines for supplying power to the respective heating elements are externally arranged to the recording head in order to drive the many heating elements, the number of wiring lines increases to complicate the electrical connection between the recording head;and a recording apparatus main assembly mounting it. For this reason, the recording head normally incorporates a driving circuit for the heating elements to prevent an increase in the number of wiring lines between the recording head and the recording apparatus. This driving circuit is arranged independently of the board of the heating elements, and they are connected by wire bonding or the like. Recently, an Si (silicon) wafer including a driving circuit has widely been used as the board of the heating elements.
This driving circuit can be variously constituted, and typical arrangements thereof will be described below.
(1) As the most popular arrangement, the driving circuit comprises a shift register having bits equal in number to heating elements, a latch circuit, gates, and transistors. Recording data is serially transferred from the recording apparatus to the shift register, and latched. This latched signal drives a transistor through a gate corresponding to a driving signal supplied for each block.
(2) In this arrangement, a diode matrix is employed. That is, heating elements are wired in an Nxc3x97M matrix, and diodes are arranged in series with the respective heating elements in order to avoid crosstalk of currents between the respective heating elements. Therefore, the number of wiring lines for connecting the recording head to the outside is only N+M.
(3) This arrangement uses a transistor matrix and a circuit in which transistors are arranged in correspondence with respective heating elements, each collector is connected to one end of a corresponding heating element, and the emitters are commonly connected. The power supply lines for the heating elements and the base signal lines for the transistors are wired in a matrix to drive them. Therefore, the number of wiring lines for connecting the recording head to the outside is larger than that of the arrangement using the diode matrix by only the common wiring line for the emitters. The transistor may be a bipolar transistor or an FET.
The above conventional driving circuits, however, have the following problems.
More specifically, although the number of wiring lines to be connected is advantageously small in the arrangement (1) having the shift register and the latch circuit, the circuit is bulky and its cost is high. Particularly, when many heating elements are used, the manufacturing yield of the driving circuit is low, greatly increasing the cost. In driving the heating elements, a large current instantaneously flows to generate strong electrical noise. In the circuit with this arrangement, since many flip-flops are driven with high-speed clocks, data in the shift register may be shifted by the noise or may change. In addition, since the heating elements are divided into a plurality of blocks, and driven at slightly different operation timings, strong noise is repeatedly generated during one data transfer, further increasing the probability of an operation error.
In the circuit using the diode matrix or the transistor matrix, no flip-flop is basically used. Even if strong noise is mixed, the circuit normally operates except the noise mixture moment. The instantaneous noise does not influence the subsequent operation, so operation errors rarely occur. Normally, while the driving time of the heating elements in one recording operation is several xcexcsec, the noise generation time is about 10 nsec, and the influence of noise can be ignored. However, in either of the two circuit arrangements, the power line must be switched at a high speed by a circuit on the recording apparatus side for driving the driving circuit in the recording head. For this reason, the driving circuit on the recording apparatus side becomes bulky and requires high cost. Further, the power loss is large due to the presence of two transistors between the power supply and ground of the recording head to perform switching on the positive and negative sides of the heating element.
In the matrix drive circuit using the diode matrix or the transistor matrix, N+M or more signal lines are required. Accordingly, the number of wiring lines for electrically connecting the recording head and the recording apparatus disadvantageously increases in the recording head, which has a large number of nozzles, i.e., drives many heating elements. As a result, the cost increases, and the reliability is degraded.
It is an object of the present invention to provide a compact, low-cost recording head with high reliability free from any operation error, and a recording apparatus using it.
To achieve the above object, according to the present invention, there is provided a recording head comprising Mxc3x97N recording elements which are divided into N blocks each having M recording elements and are driven for every M recording elements N times, Mxc3x97N driving circuits for energizing and driving the Mxc3x97N recording elements, a selection circuit for outputting N block selection signals for selecting the N blocks to be divisionally driven, an input circuit for inputting recording data corresponding to the M recording elements, and an output circuit for outputting a driving signal to the driving circuits in accordance with the recording data input from the input circuit and the block selection signals, wherein the selection circuit outputs the N block selection signals on the basis of L (L less than N) control signals.
According to the present invention, there is provided a recording apparatus comprising a recording head, the recording head comprising Mxc3x97N recording elements which are divided into N blocks each having M recording elements and are driven for every M recording elements N times, Mxc3x97N driving circuits for energizing and driving the Mxc3x97N recording elements, a selection circuit for outputting N block selection signals for selecting the N blocks to be divisionally driven, an input circuit for inputting recording data corresponding to the M recording elements, an output circuit for outputting a driving signal to the driving circuits in accordance with the recording data input from the input :circuit and the block selection signals, wherein the selection circuit outputs the N block selection signals on the basis of L (L less than N) control signals, means for supplying the recording data to the recording head, and means for supplying the L control signals to the recording head.